Process for the polymerization and copolymerization of vinyl monomers and the resin compositions obtained thereby

ABSTRACT

Vinyl monomers are polymerized and copolymerized in mass or in the gaseous phase in the presence of a water-soluble polymerization catalyst which is mixed with an inert support material and water in a small amount, such that the resin product varies in consistency from a powder to a moist cake. High yields of polymer is a desirable form are obtained by this process. Further, the support material is completely embedded in the resultant polymer, so that if the catalyst support is a reinforcing agent, in compounds which are reinforced may be obtained by this process.

United States Patent Boelet al.

[451 July 11,1972

[54] PROCESS FOR THE POLYMERIZATION AND COPOLYMERIZATION OF VINYLMONOMERS AND THE RESIN COMPOSITIONS OBTAINED THEREBY [72] Inventors:Michel Boel, Rosignano-Solvay, ltaly;

Roger Dechenne, Strombeek, Belgium [73] Assignee: Solvay 8: Cie.,Brussels, Belgium [22] Filed: June 22, 1970 [21] Appl. No.: 48,184

[30] Foreign Application Priority Data June 24,1969 France "6921207 Dec.22,1969 France ..6944530 [52] US. Cl ..260/87.5, 260/863, 260/87.1,260/875, 260/87.7, 260/887, 260/891, 260/895,

[51] Int. Cl ..C08f l/04, C08f 3/30 [58] Field ofSearch ..260/88.7,89.5, 92.8, 93.5, 260/875, 87.7, 87.1, 86.3

[56] References Cited UNlTED STATES PATENTS I 2,345,659 4/1944Downes.....- ..260/92.8

' 2,961,432 11/1960 Fikentscher et al. ..260/92.8

3,475,398 10/1969 .lobard ...260/92.8 3,538,067'11/1970 Bognar..-..260/92.8

FOREIGN PATENTS OR APPLICATIONS 1,124,237 8/1968 GreatBritain OTHERPUBLlCATlONS Bovey et al., Emulsion Polymerization, lntersciencePublishers, N.Y., (1955) pages 67, 68, 70, 71

Primary ExaminerJoseph L. Schofer Assistant Examiner-Edward J. SmithAttorney-Robert E. Burns and Emmanuel J. Lobato 57 ABSTRACT 6 Claims, 1Drawing Figure P'A'TE'N'TEDJuLn I972 v t v 575,4

Quantity of Water (9.)

A10 1.0 so so e0 Quantity of Support (9.)

PROCESS FOR THE POLYMERIZATION AND COPOLYMERIZATION OF VINYL MONOMERSAND THE RESIN COMPOSITIONS OBTAINED TIIEREBY BACKGROUND OF THE INVENTIONThe present invention concerns a' process for the polymerization and forthe copolymerization of vinyl monomers in mass or in the gaseous phaseand to the resinous compounds obtained thereby.

It is well known that mass or bulk polymerization processes, forexample, in accordance with German Pat. No. 579,048, dated June 15, 1938and in the gaseous phase, in accordance with Belgian Pat. No. 686,088,dated Aug. 29, 1966 which corresponds to copending U.S. Pat. ApplicationSer. No. 663,540, filed Aug. 28, 1967, now abandoned have advantagesover the known procedures of polymerization in aqueous emulsion, forexample, as described in French Pat. No. 746,969, dated Dec. 6, 1932 andin aqueous suspension, as described for example in British Pat. No.427,494, dated Oct.25, 1933.

Among the advantages of mass and gas phase polymerization of vinylmonomers is the fact that the polymer is obtained directly in the formof a powder without further processing such as precipitation,filtration, drying and so forth. In addition a pure polymer is obtaineddue to the absence of emulsifiers or dispersants which are employed inemulsion polymerization and polymerization in aqueous suspension'respectfully.

However, procedures involving the polymerization in mass and in the gasphase also have certain inconveniences and disadvantages. In particular,the only initiators for mass and gas phase polymerization which havebeen available are catalysts which are soluble in the monomer, such asorganic peroxides. After polymerization, catalytic residues are foundintimately mixed with the polymer and these are quite difficult toeliminate. Such residues when allowed to remain in the polymer have anunfavorable influence on the thermal stability of the resin product.

By use of water-soluble catalysts, it would be possible to remedy thisundesirable aspect of gas phase and mass polymerization, in view of thefact that the residues of such catalysts are generally not particularlyharmful to the polymer and moreover, if desired, could easily beseparated. However, water-soluble catalysts currently employed forpolymerization of vinyl monomers in aqueous emulsion have been found tobe completely ineffective for polymerization in mass and in the gasphase.

SUMMARY OF THE INVENTION A process has now been discovered for thepolymerization and for the copolymerization of vinyl monomers in mass aswell as in the gaseous phase by means of water-soluble catalysts.

It has been found, unexpectedly, that water-soluble catalysts areeffective to initiate the polymerization of vinyl polymers in masspolymerization and in polymerization in the gaseous phase when thecatalyst is combined with a small quantity of water, the quantity beingsuch that the solid product obtained as a result of the polymerizationis able to absorb the water and retain a consistency which may vary frompowder to a moist cake.

It has also been found, according to the invention, that gas phase andmass polymerization of vinyl monomer with a water-soluble catalyst ismost effective when the interface of the catalyst is as extended aspossible and that this is preferably achieved by using a supportedcatalyst.

Thus, according to the present invention, the polymerization andcopolymerization of vinyl monomers is carried out in mass or in thegaseous phase in the presence of a water-soluble catalyst which is mixedwith an inert support and a small quantity of water such that thepolymer product is obtained in a consistency which may vary from powderto a moist cake.

The support material may be a reinforcing material for the resin, andreinforced resin products may thereby be obtained.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a diagram upon which theaxis AB corresponds to the amount of support employed in grams and theaxis AC to the amount of water in grams; the lines AD, AE, AF and AHdefine the gravimetric ratios (a) of the amount of water with respect tothe amount of support. The lines AD and AE wherein (a) is 1.5 and 0.05respectively define the limits of the ratio of the weight of water tothe weight of support in the catalytic system according to the presentinvention; the lines AF and the lines AH define the preferred limits ofthe ratio of the weight of water to the weight of support in thecatalytic system according to the present process.

DESCRIPTION OF THE INVENTION According to the present invention, it hasbeen found that the polymerization of vinyl monomers can be carried outin the gaseous phase and in mass by means of a water-solublepolymerization catalyst, of the type generally employed for emulsion andaqueous suspension polymerization, providing that the catalyst iscombined with a small amount of water. However, it has also been foundthat in order for the polymerization to be initiated sufficiently andeffectively, it is necessary that the interface between the catalyst andthe vinyl monomer be as extended or spread out as possible. The catalystemployed in the present process is insoluble in the monomers undergoingpolymerization, so that it is likely that polymerization takes placeonly at the interface of the immiscible phases, i.e. the monomer phaseand the catalytic phase.

In order to achieve an extended dispersion of the catalytic phase in themonomeric phase, it has been found most effective to use a supportedcatalyst.

The catalytic support material used in the present process may be of anynature provided it does not have an inhibitory effect on thepolymerization. Thus, the supports may be selected from those currentlyemployed for this purpose, such as colloidal silica, calcium carbonate,glass fibers, nylon fibers and asbestos fibers. After polymerization,the support material is completely embedded in the resultant polymer Inthis manner and according to the present invention, polymers may beproduced which are reinforced or strengthened by various reinforcingmaterials. The support may also be a polymer of any type, mostpreferably in finely divided form, and particularly the polymer productresulting from polymerization or copolymerization according to thepresent process.

The particle size of the support material is of no importance and thesupport material may be in the form of powder, granules and fibers.Further, the ratio of support material to monomer is of no importance inthe present process; in fact, the present process may be carried outwithout support material, however, the process is more effective when asupport is used.

However, it has been found that in order to retain some of the principaladvantages of polymerization in mass and in the gaseous phase, the ratioof water to the support material, i.e. parts by weight of water to partsby weight of support, should be between about 0.02 and 1.5.

When polymerization is carried out according to the present invention,it is not necessary that the polymers be precipitated or separated fromthe reaction medium in view of the fact that the product is obtaineddirectly in the form of a solid with a consistency which may vary from apowder to a moist cake. On the other hand, depending on the specificquantity of water used, drying may not be required at all, or withrespect to a moist cake, a light drying is sufficient. Moreover, thepolymers obtained by the present process have the particular advantageof being free of harmful, noxious, organic, catalytic residues which,when present, are difficult to eliminate.

The catalysts which are employed in the present process are thewater-soluble polymerization catalysts which are currently used inaqueous emulsion polymerization of vinyl monomers. ln general,water-soluble peroxide catalysts are employed, preferably inorganicperoxides or peroxide systems such as those described by Bovey et al. inEmulsion Polymerization,

lOl044 0453 Interscience Publishers, lnc., New York, 1955, on pp. 65-81,which reference is incorporated herein. Persulfate, perborate andpercarbonate salts are preferred, particularly the alkali metal andammonium salts thereof.

In general, about 0.05 to 5 percent by weight and more preferably from0.1 to 2.5 percent by weight of catalyst is used based on the weight ofmonomer in the present process.

The present method of polymerization in the presence of a supportedcatalyst will be further described with reference to the diagram of theattached figure.

In this diagram, the axis AB corresponds to the quantity in grams of thesupport and the axis AC to the quantity in grams of the water used inthe catalyst system according to the present invention. The lines AD,AE, AF and AH correspond to constant gravimetric ratios (a) which definethe quantity of water in grams with respect to the quantity of supportin grams, wherein (a) is equal to 1.5, 0.02, 1.1 and 0.05, respectively,for the lines AD, AE, AF and AH. The lines AD and AH define the limitsof the ratio of the parts by weight of water to the parts by weight ofsupport in the catalytic system according to the present process, whileAF and AH define the more preferred limits thereof. Thus, the ratio ofthe parts by weight of water to the parts by weight of support is suchthat it must be on or between the lines AD and AE or more preferably, onor between the lines AF and AH.

For a ratio greater than 1.5, the polymer produced is generally not apowder or a cake. if the rate of conversion is low, and a ratio of waterto support greater than 1.5 is used, the polymer may be obtained in theform of soup or at best as a suspension or in aqueous latex, which thenmust be subjected to the operations of precipitation, separation andintensive drying. In this case, the advantages of polymerization in massor in the gaseous phase are lost.

if the ratio of water to support is below 0.02, the rate of conversionof vinyl compound into polymer becomes insignificant and thepolymerization process is impractical.

The process of the present invention is applicable to polymerization andto copolymerization of vinyl monomers wherein the polymerization iscarried out in mass and in the gaseous phase. Vinyl chloride, vinylacetate, styrene, acrylonitrile and alkyl acrylates and methacrylatesmay be mentioned among the vinyl compounds which are desirablypolymerized according to the present invention. The present process isespecially desirable for the preparation of the homopolymers of vinylchloride and copolymers of vinyl chloride which contain at least a majorproportion of vinyl chloride. In particular, vinyl chloride may becopolymerized with vinylidene halides, such as vinylidene chloride,vinyl esters, such as vinyl acetate, aromatic vinyl monomers, such asstyrene, acrylic monomers such as acrylonitrile, alkyl acrylates andmethacrylates, and olefms in general, such as ethylene, propylene,butene-2, chlorinated olefins, such as vinyl fluoride and vinylidenefluoride.

Aside from the new and improved catalytic system used according to thepresent invention, any known procedure of mass polymerization orpolymerization in the gaseous phase can be used within the scope of thepresent invention. For example, the procedure for polymerization in massas described in German Pat. No. 579,048, dated June 15, 1928, may beemployed or the process of polymerization in the gaseous phase,described in Belgian Pat. No. 686,088, dated Aug. 29, 1966, may beemployed.

When operating in mass or bulk, the polymerization pressure is equal toor greater than the saturated vapor pressure of the monomer undergoingpolymerization. The saturated vapor pressure of course depends upon theoperating temperature. In the case of the mass polymerization of vinylchloride, for example, it is preferable to operate at about 40 to 80 C.and under a pressure such that the ratio of the polymerization pressure(kg./sq.cm.) to the saturated vapor pressure (km/sq.cm.) is equal to orgreater than 1.

On the contrary, when polymerization is carried out in the gaseousphase, the operating pressure is lower than the saturated vapor pressureof the monomer at the temperature of polymerization. Thus, thepolymerization of vinyl chloride in the gaseous phase is preferablycarried out at about 40 to C. wherein the relative pressure (defined bythe above-mentioned ratio) is greater than 0.45 but lower than 1.

The following examples further illustrate the best mode currentlycontemplated for carrying out the present invention; however, theexamples must not be construed as limiting the scope of the invention inany manner. Examples which include the letter R" have been included forpurposes of comparison and do not illustrate the present invention.

EXAMPLE 1R Ammonium persulfate in an amount of 2.5 g. is introduced intoa polymerization autoclave having a capacity of l l. and

equipped with a stirring apparatus. The air contained in the autoclaveis eliminated by means of a vacuum and it is replaced with nitrogenuntil an effective pressure, (i.e. (i.e. pressure above atmosphericpressure of 0.6 kg./sq.cm. is reached. Immediately prior to theintroduction of the monomer, the autoclave is again placed under vacuum.Then, 450 g. of liquid vinyl chloride are introduced and the mixture isheated at 55 C. and stirred at 250 rpm.

The operation is carried out under an effective pressure of 8.1kg./sq.cm., that is, just above the saturated vapor pressure ofthe vinylchloride at 55 C., i.e. 8 kg./sq.cm.

After 7 hours under the above-mentioned conditions and after degassing,it was found that no polymer had been produced.

This example shows clearly that in the absence of water, a water-solublecatalyst is completely ineffective for the mass polymerization of vinylchloride EXAMPLES 2 to 4 These examples refer to the polymerization ofvinyl chloride in mass in accordance with the process of the presentinvention. The operation is carried out in the same manner as ExamplelR. The operating conditions and the results are set forth in Table 1shown hereinafter.

EXAMPLES 5 to 23, 24R and 25R Examples 5 to 23 involve the masspolymerization of various vinyl monomers in accordance with the processof the present invention in the presence of a catalyst system composedof an aqueous solution of a water-soluble catalyst which has beenpermeated on an inert support.

In these examples, the catalytic system is prepared in the followingmanner: The support is introduced into a cylindrical round-bottomcontainer equipped with agitating means; after the support has beenmixed, the aqueous solution of the catalyzer is introduced drop by drop;the mixture obtained in this manner is then agitated over a period of afew minutes in order to obtain a homogeneous mixture. Then, theoperation is carried out in the same manner as in Example 1 Examples 24Rand 25R are provided for purposes of com- The catalytic system isprepared as described in Examples 5 parison. In these examples,polymerization has been carried to 25R. out under the same conditions asin Examples 5 to 23, but the Th ati i carried out in the same manner asExample ratioof r/ pp is p ly, 4 n ioutside 1R until the finalapplication of vacuum to the autoclave After that of the catalyst systemused in the PF of the invention 5 this step, instead of introducingliquid vinyl chloride, gaseous Undel' these conditions the resulting P yis an aqueous vinyl chloride is introduced while agitation is maintainedin SOuplike mixture requiring sepat'ation and drying treatments, theautoclave until an effective pressure of l kg./sq.cm. is which is 'y tothe result sought y the Present p reached. The temperature of themixture in the autoclave is The Perattng conditions and the results ofthese examples increased until the operating temperature is reachedwhile the are Set forth in Table l mixture is constantly agitated. Thepolymerization autoclave TABLE 2 Examples 5 6 7 8 U 10 11 12 13 14 15 16Conditions of operation and results:

Monomer, g.:

Vinyl chloride y Acrylonitrile Catalyst system:

Ammonium persulfatc, g 0.5

U. 5 0. 5 Sodium perborate, g Sodium percarbonate, g Water, g 7. 5 48 88 18 2O 20 .20 20 Support, 51.:

Colloidal silica 47 47 47 47 47 47 47 47 47 Fiber glass" Asbestosfibers. N ylon fibers Precipitated calcium carbonate .l Ratio of weightof water to weight of support.- Conditions of polymerization:

Temperature, C 55 55 55 55 55 55 55 55 55 55 55 55 Effective pressure,kg./sq.cm 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 9. 2 Speed oi agitation,r.p.1n.. 250 250 250 250 250 250 250 250 250 250 250 250 Period ofpolymerization, h 3 3 1.67 3 3 2 3 3 3 Type of procedure l. Mass MassMass- Mass Mass Mass Mass Moss Mass Mass Mass Mass Polymer product Totalquantity, g 49. 5 146. 5 69. 5 100 233 20. 5 l8. 5 21 38 6 25. 5 114. 5Quantity per hour, g./h,. Appearance Powder without free water Examplesl 17 18 19 l 20 21 22 23 24R 25R Conditions of operation and results:

Monomer, g.:

Vinyl chloride A 450 450 450 450 450 1, 350 150 l, 350 41! PropyleneStyrene Methyl metltacrylate Acrylonitrile Catalyst system:

Ammonium pcrsulfate, g Sodium perborate, g..-. Sodium percarbonate, g..,Water Su port, gs.

Iolloidal silica 47 Fiber glass Asbestos fibers. Nylon fibers.Precipitated calcium carbonate Ratio of weight of water to. weight ofsupport Conditions of polymerization:

Temperature, C .1 55 55 55 55 55 55 55 55 Ell'ectlve pressure, kg./sq.cm8 B 8 ti 8 3 3 g 8 Speed of agitation, r.p.rn...

Period oi polymerization, h. 3 2. 78 2 1.67 3, 5 2 2. 5 2:5 '1 ype ofprocedure Mass Moss Mass Mass Mass Mass Mass Aqueous mixture Polymerproduct:

Total quantity, 5 '24. 5 128 82. 5 J2. 2 125 82. 5 153. 5 162 Quantityper hour, g./h. 3.8 8. 2 46.1 41. .2 55.2 35. 7 41 61.5 64. 8 AppearancePowder without free water Soupy Soupy Quantity of support deducted.

EXAMPLES 2 to 33 is connected to an autoclave filled with monomermaintained at a temperature which is from 2 to 3 C. lower than the Theseexamples involve a number of gaseous phase polymerization temperature.The transfer of the monomer is polymerizations of vinyl chloride inaccordance with the effected gradually asthe polymerization in gaseousfonn takes process of the present inventio wherei a catalyst systemplace to mamtam the desired pressure in the autoclave. The containing anaqueous solution of water-soluble catalyst and 3 operation conditionsand the results of the polymerization are support are employed. Setforth in Table 3.

" i TABLE 3 Examples 26 27 28 29 30 31 32 33 Conditions of operation andresults:

Catalyst system:

Ammonium persulfate, g 0.1 Water, g 70 Supports, g.:

Colloidal silica 70 Polyvinyl chloride Ratio olwei ht ofwater to weightofsupport..

Conditions of po ymerization:

Temperature, C Effective pressure, kg./sg. cm Speed of agitation, r.p.mPeriod of polymerization, h

Polymer product:

Quantity, g Quantity per hour, g./h

Appearance Quantity of support deducted.

What we claim as new and desire to secure by Letters Patent is:

1. Process for the homopolymerization of a vinyl monomer selected fromthe group 0 onsisting of vinyl chloride, vinyl acetate, styrene,acrylonitrile and alkyl acrylate and methacrylate and for thecopolymerization of vinyl chloride with monomers selected from a memberof the group consisting of vinylidene halide, .vinyl ester, an aromaticvinyl 'monomer, acrylic monomer, olefin and vinyl fluoride in mass 2.Process according to claim 1 in which said support is permeated with anaqueous solution of the said catalyst and in which the ratio of thequantity of water to the quantity of support is about 0.05 to 1.1.

3. Process according to claim 1 in which said inert support is areinforcing material which adds strength to the resin product.

4. Process for polymerization according to claim 1 in which said supportis permeated with an aqueous solution of said catalyst and in which saidsupport is selected from the group consisting of colloidial silica,glass fibers, nylon fibers, asbestos fibers, calcium carbonate and avinyl polymer.

5. Process according to claim 1 in which vinyl chloride is copolymerizedwith an olefin.

6. Process according to claim 1 in which the vinyl monomer, selectedfrom the group consisting of vinyl chloride, styrene, acrylonitrile,alkyl acrylate and alkyl methacrylate, is homopolymerized.

2. Process according to claim 1 in which said support is permeated withan aqueous solution of the said catalyst and in which the ratio of thequantity of water to the quantity of support is about 0.05 to 1.1. 3.Process according to claim 1 in which said inert support is areinforcing material which adds strength to the resin product. 4.Process for polymerization according to claim 1 in which said support ispermeated with an aqueous solution of said catalyst and in which saidsupport is selected from the group consisting of colloidial silica,glass fibers, nylon fibers, asbestos fibers, calcium carbonate and avinyl polymer.
 5. Process according to claim 1 in which vinyl chlorideis copolymerized with an olefin.
 6. Process according to claim 1 inwhich the vinyl monomer, selected from the group consisting of vinylchloride, styrene, acrylonitrile, alkyl acrylate and alkyl methacrylate,is homopolymerized.